Speed reducer

ABSTRACT

A speed reducer includes an input shaft, an output shaft, and a gear assembly coupled to the input shaft. The gear assembly includes a housing, an external gear, and at least two internal gears. The external gear is located within the housing and inscribes the at least two internal gears. One side of the at least two internal gears is rotatably coupled to the input shaft, and another side of the at least two internal gears is coupled to a connecting column of the output shaft. The at least two internal gears are offset on the input shaft, and the input shaft drives the at least two internal gears to maintain engagement with the external gear. The connecting column maintains transmission of the output shaft and the at least two internal gears.

FIELD

The subject matter herein generally relates to a speed reducer.

BACKGROUND

Generally, precision tools, automatic equipment, and robotic componentrequire a speed reducer to change speeds and transmit torque.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present disclosure will now be described, by wayof example only, with reference to the attached figures.

FIG. 1 is an assembled, isometric view of an embodiment of a speedreducer.

FIG. 2 is an exploded, cross-sectional view of the speed reducer of FIG.1.

FIG. 3 is a cross-sectional view of the speed reducer of FIG. 1.

FIG. 4 is an isometric view of the speed reducer of FIG. 3.

FIG. 5 is a front view of the speed reducer of FIG. 1.

FIG. 6 is a cross-sectional view of an internal gear and a connectingcolumn of the speed reducer of FIG. 1.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The term “coupled” is defined as connected, whether directly orindirectly through intervening components, and is not necessarilylimited to physical connections. The connection can be such that theobjects are permanently connected or releasably connected. The term“comprising” means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in aso-described combination, group, series and the like.

FIG. 1 illustrates an embodiment of a speed reducer 100. The speedreducer 100 includes an input shaft 10, a gear assembly 20, and anoutput shaft 30. The input shaft 10 and the output shaft 30 are locatedat opposite sides of the gear assembly 20 and reduce the volume and sizecooperatively of the speed reducer 100. Referring to FIG. 2, the inputshaft 10 is an offset shaft. The input shaft 10 is coupled to the gearassembly 20. The gear assembly 20 includes a housing 22, an externalgear 24, and at least two internal gears 26. The external gear 24 isreceived within the housing 22. The external gear 24 inscribes theinternal gears 26. One side of the internal gears 26 is rotatablycoupled to the input shaft 10, and another side of the internal gears 26is coupled to a connecting column 32 of the output shaft 30. The inputshaft 10 drives the internal gears 26 to maintain engagement with theexternal gear 24, and the connecting column 32 maintains transmission ofthe output shaft 30 and the internal gear 26. The input shaft 10includes at least two offset pieces 101 arranged on the input shaft 10.The at least two offset pieces 101 are rotatably coupled to the internalgears 26 through a sleeve 12 (shown in FIG. 3) to cause the internalgears 26 to engage with the external gear 24. In at least oneembodiment, the input shaft 10 includes two offset pieces 101. Theoffset pieces 101 are offset relative to each other on the input shaft10. In other words, the offset pieces 101 are positioned 180 degreesapart from each other on the input shaft 10 to cause the internal gears26 to engage with the external gear 24. In detail, the internal gears 26includes a first internal gear 261 and a second internal gear 263. Thefirst internal gear 261 is adjacent to the input shaft 10, and thesecond internal gear 263 is adjacent to connecting column 32 of theoutput shaft 30. The first internal gear 261 and the second internalgear 263 each engage with the external gear 24 at opposite sides of theinput shaft 10. The input shaft 10 and the output shaft 30 are locatedon opposite sides of the gear assembly 20, and the housing 22 of thegear assembly 20 fixes the external gear 24. The output shaft 30 isreceived in the housing 22 through a bearing 301.

Referring to FIG. 3, the external gear 24 is an annular gear. The firstinternal gear 261 and the second internal gear 263 are located withinthe external gear 24. The first internal gear 261 and the secondinternal gear 263 engage with the external gear 24 on opposite sides ofthe external gear 24. Thus, when a driving shaft 40 of a motor (notshown) is rotatably coupled to the input shaft 10, the driving shaft 40drives the input shaft 10 to rotate. The input shaft 10 drives the twooffset pieces 101 to drive the first internal gear 261 and the secondinternal gear 263 to rotate. The first internal gear 261 and the secondinternal gear 263 rotate within the external gear 24. The external gear24 is fixed to the housing 22 (as shown in FIG. 1) and cannot rotate.The first internal gear 261 and the second internal gear 263 rotatingwithin the external gear 24 have a tooth difference with the externalgear 24. The tooth differences of the first internal gear 261 and thesecond internal gear 263 with the external gear 24 may be the same ordifferent. An output torque results from the tooth differences and isoutput through the output shaft 30 coupled to the second internal gear263.

Referring to FIG. 4, the first internal gear 261 and the second internalgear 263 engage with the external gear 24 at points of contact andmaintain engagement through a tooth profile. In at least one embodiment,the tooth profile of the first internal gear 261 and the second internalgear 263 engaged with the external gear 24 is a round tooth profile. Thefirst internal gear 261 and the second internal gear 263 engage theexternal gear 24 at rounded contact points. In another embodiment, thefirst internal gear 261 and the second internal gear 263 may have atriangular tooth profile or a tooth profile of other shapes with theexternal gear 24. In detail, the first internal gear 261 and the secondinternal gear 263 are adjoined together and arranged 180 degrees apartfrom each other on the input shaft 10. Thus, the first internal gear 261and the second internal gear 263 are configured to engage with theexternal gear 24 180 degrees apart from each other. As shown in FIG. 5,the first internal gear 261 and the second internal gear 263 each arespaced apart 180 degrees from each other to engage with the externalgear 24. In addition, an axis of the input shaft 10 and an axis of theoutput shaft 30 are coaxial along a same horizontal line, and the firstinternal gear 261 and the second internal gear 263 are driven by theinput shaft 10. The first internal gear 261 and the second internal gear263 achieve gapless transmission with the external gear 24. The drivingshaft 40 drives the input shaft 10 to rotate, which causes the firstinternal gear 261 and the second internal gear 263 to achieve gaplesstransmission with the external gear 24, and the output shaft 30 outputszero-gap transmission of torque.

Referring to FIG. 4, a side of the second internal gear 263 adjacent tothe output shaft 30 includes a connector 2631. The connector 2631extends from the second internal gear 263 toward the connecting column32. An interior of the connector 2631 defines a plurality of equallyspaced apart scarf holes 2633. The scarf holes 2633 are elongated andarranged radially along the connector 2631. In detail, the connector2631 is located on a side of the second internal gear 263 facing theoutput shaft 30. The interior of the connector 2631 defines theplurality of scarf holes 2633. The connecting column 32 is located on anend of the output shaft 30 and includes a plurality of protrusions 321.The protrusions 321 correspond to the scarf holes 2633. The protrusions321 protrude from the end of the output shaft 30 and are inserted intothe corresponding scarf holes 2633. Thus, rotation of the secondinternal gear 263 is transmitted through the protrusions 321 insertedinto the scarf holes 2633 to the output shaft 30. Finally, the secondinternal gear 263 is rotated offset. The protrusions 321 inserted intothe scarf holes 2633 maintains connection between the second internalgear 263 rotating and the output shaft 30 to precisely output torquetransmission. In other words, the plurality of protrusions 321 insertedinto the plurality of scarf holes 2633 throughout the offset rotation ofthe second internal gear 263 maintain zero-gap output torque between thesecond internal gear 263 and the output shaft 30.

The speed reducer 100 uses the offset configuration of the firstinternal gear 261 and the second internal gear 263 and the protrusions321 inserted into the scarf holes 2633 to realize zero-gap transmissionand high-precision and steady output torque.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

What is claimed is:
 1. A speed reducer comprising: an input shaft; anoutput shaft; and a gear assembly coupled to the input shaft andcomprising a housing, an external gear, and at least two internal gears,the external gear located within the housing, the at least two internalgears connected inside the external gear and comprising a first internalgear and a second internal gear, one of the sides of the first internalgear rotatably coupled to the input shaft, one of the sides of thesecond internal gear coupled to a connecting column of the output shaft;wherein the second internal gear comprises a connector extending fromthe one of the sides of the second internal gear toward the connectingcolumn of the output shaft, the connector is coupled to the connectingcolumn; wherein the input shaft is an offset shaft; wherein the inputshaft drives the at least two internal gears to maintain engagement withthe external gear; and wherein the connecting column maintainstransmission between the output shaft and the at least two internalgears.
 2. The speed reducer of claim 1, wherein the input shaftcomprises at least two offset pieces positioned offset to each other onthe input shaft; each of the at least two offset pieces are rotatablycoupled to a respective one of the at least two internal gears through arespective sleeve to cause the at least two internal gears rotatablycoupled to the at least two offset pieces to engage with the externalgear.
 3. The speed reducer of claim 2, wherein the two internal gearsrotatably coupled to the at least two offset pieces separately engagewith the external gear on opposite sides of the input shaft.
 4. Thespeed reducer of claim 1, wherein the first internal gear is adjacent tothe input shaft; the second internal gear is adjacent to the connectingcolumn of the output gear; the input shaft and the output shaft arelocated at opposite sides of the gear assembly; and the housing of thegear assembly is fixed to the external gear.
 5. The speed reducer ofclaim 4, wherein the external gear is an annular gear; the firstinternal gear and the second internal gear are located within theexternal gear; the first internal gear and the second internal gearengage with the external gear at opposite sides of the input shaftwithin the external gear; the first internal gear and the secondinternal gear are engaged with the external gear with a toothdifference, the tooth difference is a difference in number of teeth ofthe first internal gear and the second internal gear; an output torqueresults from the tooth difference.
 6. The speed reducer of claim 5,wherein the first internal gear and the second internal gear are engagedwith the external gear at points of contact; engagement of the firstinternal gear and the second internal gear with the external gear ismaintained by tooth profiles of the first internal gear and the secondinternal gear engaged with the external gear.
 7. The speed reducer ofclaim 6, wherein the tooth profiles of the first internal gear and thesecond internal gear engaged with the external gear are round toothprofiles; the first internal gear and the second internal gear engagewith the external gear at an interval of 180 degrees relative to eachother.
 8. The speed reducer of claim 4, wherein an interior of theconnector defines a plurality of scarf holes; the plurality of scarfholes are formed by a plurality of spaced ribs of the second internalgear, the plurality of spaced ribs are elongated and arranged radiallyalong the connector.
 9. The speed reducer of claim 8, wherein theconnecting column is located at one end of the output shaft andcomprises a plurality of protrusions each corresponding to acorresponding one of the scarf holes; the protrusions protrude from theend of the output shaft toward the scarf holes.
 10. The speed reducer ofclaim 9, wherein the protrusions of the connecting column are insertedinto the corresponding scarf holes of the connector; rotation of thesecond internal gear is transferred through the protrusions insertedinto the scarf holes to the output shaft.